Suggestion: Macron MPT-xxx and MPT-xxx2

[LongRunner]

I've added the datasheet for the WT7525 to my previous post.

[c_hegge]

Nice! It even supports Dual 12V OCP, so it looks like it is genuinely a dual rail.

[c_hegge]

Here's an internal shot of my MPT-4012. It looks quite capable of the labelled 400W. It just needs a recap.

[LongRunner]

It's been a while, but I've found a few nits to pick with the family:

Original MPT series

• The mains wires were of the reinforced type (UL AWM style 1617, which has both the thick inner insulator like style 1015 but also a thinner outer jacket for added safety), which is good as they can be in fairly close proximity to the secondary side of the unit (and indeed can touch the secondary heatsink — which, for that matter, was not earthed as it is in many units including the following generation — very easily). But while I appreciate the use of a mains connector, the connector they chose is not designed for wire with such a large outer diameter and while the conductors are crimped fine, Macron's attempt at crimping the outer jacket was kind of ugly. All it would have taken to do it properly would have been to remove about 5~10mm of the outer jacket from the leads where they are attached to the connector.
• CY1 (one of the Y capacitors on the main PCB) tends to be installed with one of its leads in a hole for R1 (a bleed resistor for the X capacitor on the main PCB that was provided for but never installed as the additional filter board already has one) instead of the intended hole. Functionally, it doesn't matter as it connects to the same part of the circuit anyway, but it does look somewhat unprofessional.
• At the upper end of the normal mains voltage range, the bleed/divider resistors across the primary capacitors are running fairly close to their power rating (they are 150kΩ ±5% carbon film and appear to be 0.25W going by the size; with the European/Australian upper limit of 253VAC, there is 178VDC or so across each resistor and they dissipate about 0.21W each). There is no discolouration of the PCBs that I've seen, so the beefy traces in the area seem to do a fair job of conducting that heat away, but I do think it's an ever-so-slightly bad idea to go that close to the rating of resistors whose failure would be the end of one of the primary capacitors. Their counterparts in my MPT-4012 appear to be identical.
• In the earlier 80mm-fan version, which had a mains pass-through outlet, the wiring arrangement placed that outlet between the two stages of the EMI filter. This has two implications — some common-mode noise will make it into whatever is plugged into that outlet (though I doubt most common loads would be adversely affected) when the PSU is active, and if too much current is drawn through that outlet (especially with the unit in standby mode), the filter choke could get rather hot.

MPT 2 series (not that I've found another unit, but the PCB does hint at models from 300W up to 500W)

• The original MPT series had a ceramic fuse in a holder, but all we get this time is a cheap glass fuse soldered directly to the PCB (though the through-holes for fuse clips are still provided). The NTC thermistor is clearly marked as 2.58Ω cold (though my DMM reads 3.3Ω…), so might just allow the fuse to contain itself when cold, but with the thermistor hot…?
• The datasheet for the WT7525 suggests that capacitors of at least 1µF be installed between the current sense and voltage sense pins to prevent nuisance tripping of the OCP, and they are all provided for on the underside of the PCB, but none of them were installed.
• Possibly as a result of realising that the mains-to-PCB connector they use isn't designed for the thick reinforced wires they used last time, this time they used single-insulated mains wires (UL AWM style 1015 as mentioned) and instead chose a non-shrinkable tube to provide the extra layer of insulation in the vicinity of the secondary side (the only reinforced wire remaining is that from the first stage of the filter to the main switch). But (in my unit, anyway) the sleeve fails to stop the active/line wire to the board from touching the top of one of the +3.3V caps (the one before the ferrite coil), so it looks like they could have done with a bit of heat-shrinkable tubing there (or simply use the reinforced wire again, but strip the jacket where appropriate). (Fortunately, you can simply use a shorter 12.5mm diameter replacement cap and avoid that bit.)

(Ugh…this Waterfox is eating a whole thread worth of CPU time and running at a snail's pace for some damn reason. What do you think the best alternative would be?)

[LongRunner]

Some hope for a review of an MPT-301 remains, as I have one that appears to work normally. This one has the Auriga brand with a green logo (for the version with the better casing; the version with the other casing has a blue logo, and the ATX9806B-P has, rather fittingly, a red logo). There are two other nits that I can think of to pick with the series ‒ they didn't seem to pay any attention to positioning vertically mounted resistors as the silkscreen indicates (with the resistor body often on the wrong side), and the earth connections in some of the original 80mm-fan units (including this one) lack tooth washers and rely on only the locking screw heads to keep them in place (at least, when they switched to 120mm fans, they made the earth connection more solid). Neither of these is that big of a deal (probably the biggest one mentioned is the downgraded fuse in later generations), but I thought it worth mentioning anyway.

The ATX9806B-P (which I've only seen with the Auriga brand, red logo) is rather wimpy in comparison to the MPT series (even more so compared to the later generations). The rating given is 300W, which looks too much to ask. The mains wires here are only single-insulated (except for the one from the first stage of the EMI filter to the main switch) and the two earth wires were squeezed into a single eyelet connector (instead of using a separate one for each wire), the fuse is a glass type soldered to the PCB, and the main PCB has 1kV ceramic caps instead of Y2 types . Four 2A diodes make up the primary rectifier (this would suffice for a 200W unit on 230V, but that's about it), and the primary capacitors here are only 470µF. The main switchers are 2SC4242s (7A) vs. at least 2SC2625s (10A) in the MPT series, and both heatsinks are much smaller. The main, drive, and standby transformers are EI-33, EE-16 and EEL-16 respectively, vs. ERL-35, EEL-16 and EEL-19 in the MPT series. The secondary rectifiers are an SBL1640CT for +3.3V, an SBL3040PT for +5V, and an STPR1020CT for +12V, all of which are just enough for the label ratings (14A/30A/10A respectively). The secondary capacitors are a single 2200µF 16V 13mm each on +3.3V and +12V and a combination of two 1000µF 16V and one 2200µF 10V (all 10mm) on +5V (no ferrite coils on any main rail); the low-current rails have the same configuration as in the MPT series. The fan is a sleeve bearing Power Logic as usually used in the MPT series, and is probably the most decent part of the unit.

[c_hegge]

If you want to send it my way, then PM me, and I'll stick it in the el-cheapo PSU roundup.

[LongRunner]

I should add that the 2200µF 10V caps in this particular unit are G-Luxon LZ (low ESR). The others, though, are GP (a mixture of GoldLink, Fuhjyyu TNR, and CEC-ECAP TUR series). My guess is that the ripple will be well suppressed on +3.3V and +5VSB, somewhat higher but still in spec on +5V, and borderline on +12V (I may suggest retrying with a Chemi-con KY/Nichicon HE there after the review, to see how it would have fared with a low ESR capacitor there — presuming the unit makes it through the tests without blowing up, which is up for grabs).

Given the relatively weak +12V rectifier (a U16C20C in this unit), I suggest that (if you make it to the overload test) you overload the +3.3V and +5V rails instead, as they have nice big rectifiers (good for double the label rating of each).

I'll guess at a partial score of… 3 points off for the capacitors (knowing about GP caps would make another point off for the +12V ripple ever-so-slightly redundant). Half a point off for the wimpy +12V. Maybe another half point off for the Superred fan in this one, leaving 6 points remaining for you to subtract from as desired.

[c_hegge]

I'll guess at a partial score of… 3 points off for the capacitors (knowing about GP caps would make another point off for the +12V ripple ever-so-slightly redundant).

That's about right. If there are any fuhjyyus then 3 points usually come off.

Half a point off for the wimpy +12V.

A full point. I'm totally, utterly sick and tired of 5V heavy designs. They should have been well and truly gone from the market years ago.

Maybe another half point off for the Superred fan in this one, leaving 6 points remaining for you to subtract from as desired.

Probably no points off. Superred fans are usually pretty good.

Either way, though, we still end up at 6.

[LongRunner]

A full point. I'm totally, utterly sick and tired of 5V heavy designs. They should have been well and truly gone from the market years ago.

I would agree if it was a new-ish unit, but it's over a decade old (though wasn't in use for the whole time) so for its time, it wasn't too bad. Of course, that part makes it somewhat doubtful that the caps are still OK, but I still suppose I could take a shot with it (in the next few weeks or months).

[Wester547]

Superred fans aren't lubricated well at all and aren't easy to maintenance so I don't consider them better than ADDA. G-Luxon LZ, Fuhjyyu, Goldlink, and TURD capacitors? Could definitely do well with a recap (after the review).